RE: https://hachyderm.io/@nedbat/116150179474021938

The answer to the mystery: because my function had a `yield` in it, it was compiled as a generator. But executing the function never ran `yield`, so iterating it produced an empty sequence. The value from the return statement is ignored.

TBH, I know there is a way to get the returned value, but I have never needed to, and I don't know how.

The solution was to delete the code after the return.